This invention relates to electromagnetic projectile launchers and more particularly to such launchers with a rail geometry which provides an augmented electromagnetic field in the breech area.
Electromagnetic projectile launchers are known which comprise a pair of conductive rails, a sliding conductive armature between the rails, and means for commutating a large direct current into the rails and through the armature. Current flow places an electromagnetic force on the armature which propels it along the conductive rails. An early launcher employing this concept is disclosed in U.S. Pat. No. 1,370,200, dated Mar. 1, 1921.
Prior to acceleration, conductive armatures are either stationary in the rail breech area or are inserted into the breech area at a relatively slow velocity. In order to develop an electromagnetic launcher capable of rapid firing, a technique for initiating projectile motion without damaging the projectile armature or the breech rail section is essential. The early stages of acceleration are most critical in this regard since high current density current transfer is most difficult to achieve without damage at zero or very low velocities. Copending application Ser. No. 137,059, filed Apr. 3, 1980 by Kemeny and Litz, now U.S. Pat. No. 4,347,463 entitled "Electromagnetic Projectile Launcher With Self-Augmented Rails", and assigned to the present assignee, discloses a launcher which employs additional conductors parallel to the rails to increase force on an armature for a given rail current. These additional conductors can run the full length of the rails and add significant resistance and inductance to the rail system. The present invention seeks to increase armature acceleration in the breech area for a given rail current to minimize rail and armature damage. This is accomplished with relatively short breech augmenting rail configurations, thereby minimizing resistive and inductive effects of the augmentation. Limiting augmentation to the breech area also minimizes launcher weight at the muzzle end thereby maintaining launcher maneuverability. Both parallel and nonparallel rail geometries are used to achieve breech augmentation. Since augmentation occurs during current commutation into the breech, peak acceleration of the armature and projectile need not be increased.
This invention comprises: a pair of conductors in the form of rails; a movable conductive armature between these rails; a source of high current; a switch for commutating this current to the rails and armature; and means for increasing the magnetic field in the breech area comprising, a breech augmenting conductor rail assembly which increases the electromagnetic force on a projectile in the breech area for a given current. One embodiment of this breech augmenting rail assembly comprises additional rails which are parallel to the first pair of rails and located near the breech section. These additional rails are located adjacent the pair of conductive rails and carry current in a direction which augments the electromagnetic field in the breech area.
A second embodiment of the breech augmenting rail assembly provides for augmentation of the electromagnetic field in the breech area through the use of a nonparallel rail geometry where the pair of conductive rails are bent at an angle near the breech area. This produces a repulsive magnetic field between a section of rail and the movable armature which serves to increase initial armature acceleration.